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Find which factor has the greatest effect on deciding the planform of the River Arrow in Herefordshire, by studying slope angle and discharge amongst other varying elements.

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Introduction

Kristina Gilbert Geography A-level Coursework River Study Introduction Study Area Method Pg 3 Pg 5 Pg 6 Introduction The overall aim of this investigation is to find which factor has the greatest effect on deciding the planform of the River Arrow in Herefordshire, by studying slope angle and discharge amongst other varying elements. Rivers are a primary feature of the world's surface area. Hundreds of networks of river channels together drain almost 70 percent of the earth's land surface and their characteristics differ from location to location and also at the same location over a time period, known as a river regime. In order to fully investigate the main question of this investigation, a number of subsidiary questions have been devised. Each of these in turn will help to provide answers in investigating the reasons for variation in planform. * 1. How does the planform vary along the river? * 2. Is the slope angle steeper on meandering bends than on straight sections? * 3. How do discharge and velocity compare on different planforms? * 4. Does Channel roughness effect planform? * 5. Does Landuse on the banks influence the planform shape? Turbulent flow is the major flow type in most natural river channels. It is this which justifies their efficiency in both the eroding and transporting of materials and sediment. The velocity of a river is affected by three main things, channel roughness, channel shape and gradient. ...read more.

Middle

Streams with a low sinuosity, which are comparatively straight, are associated with areas of a gentle gradient. "Their low sinuosity is a reflection of their aimless plan where sluggish downstream water velocity has not imposed a regular meander pattern on the system." (Challenge of the Natural Environment, Knapp, Ross and McCrae) Study Area: The River Arrow, Herefordshire The river Arrow, is a tributary of the river Lugg which in turn is a tributary of Herefordshire's largest river, the Wye. The Arrow is a relatively small river and so this meant that it would be safe to take readings from. I chose to focus on a small area of the Arrow near to Kington, one of Herefordshire's market towns. It is situated between the river Arrow and its tributary the Gilwern Brook. The landuse around the river in the area around the Kington area is very similar, most of it being fields for the grazing o livestock, although there are small areas of woodland either side of the town. The town centre is set away from the river's banks and so there has been very little development along the river barring a few houses and a small campsite. Method: Sampling Strategy: When deciding how to collect the field data required to carry out this investigation, it is important that the process is both practical and efficient, and therefore needs to be planned well. ...read more.

Conclusion

Velocity (in m/sec) In finding velocity a flow meter should be used, placing approximately two thirds of the depth beneath the waters surface for one minute and recording the result, which will show you how many revolutions the propeller has turned. By doing this three times across the width of the river at regular intervals you will get a reading across the whole of the river. These count figures can then be added together and divided by three to get an average. This is then used alongside a mathematical equation which will give the velocity reading: Velocity = (0.144 * count) +5. To obtain the answer in m/s as apposed to cm/s you would then divide your answer by 100. Pebble Size (in cm) Pebble size should also be recorded when depth readings are taken, at each given depth, ten regular intervals across the river, a systematic sample the pebble on the river bed should be measured by its B axis. This sampling method is appropriate as it should give fair results, with pebble sizes across the whole width of the river Secondary Data Collection Gradient (in degrees) The gradient will be measured through taking readings from contour lines on a map. By taking the measurement this way an exact reading will be given, providing the sites are marked definitely on the map. It is sometimes not possible to take gradient readings when in the field as the banks can be inaccessible. The use of an OS map subtracts any chance of unsuccessful readings on the day due to physical obstacles. 1 ...read more.

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